This invention relates generally to rod holders for coating doctors and more particularly to a new and novel design of a rod holder having a novel cooling water chamber formed beneath the rod.
In the design and use of polyethylene rod holders, it is known that the life of such holders is very short. The short life results from design features of the various holders and in particular the material used in the construction of the holder. Because of the complicated mountings utilized on prior art holders, excessive changeout time is required whenever it is desirous of changing either the holder or the rod.
A known prior art design utilizes a rod encapsulated in a polyethylene holder with only a small surface of the rod sticking out of the holder. Cooling water is fed into the ends of the rod holder with the inner part of the vein being closed by the rod. The flow of cooling water is then in one end of the holder and out of the other end. Because of the shallowness of the vein depth and as a result of the distance across the paper machine on which the coating doctor is used exceeds the length of 14', high pressures are required to maintain water flow through the holder. It follows naturally that as a result of the high pressures, leakage is experienced in the doctoring portion of the rod. A reduction in the pressure may result in the vein becoming plugged and the increased friction between the rod and the paper web may ruin the polyethylene holder.
One of the problems inherent in the before mentioned prior art holder was the material being used to construct the holder which would not tolerate heat in the range to which it was subjected and further the position of the veins weakened the overall structure of the holder. A further problem resulted in the position in which the veins were cut making it difficult to prevent leakage. A wrap around design which was utilized made it difficult to change out the rods and the metal support holder. The holder was attached to the polyethylene holder by a complicated dove-tailed design. Further problems were experienced since the vein depth restricted the volume of water that could be put through the holder for cooling, cleaning and lubrication and the distance that the water was being forced through the holder interior resulted in high pressures being required.
By referring to FIGS. 1 and 2 of the drawings there can be seen illustrations of a typical prior art rod holder and more specifically showing the interior construction of the cooling water channels. FIG. 1 is a broken perspective view of a typical prior art rod holder while FIG. 2 is a sectional view along line 2--2 of FIG. 1 showing the interior construction of the rod holder and in particular the configuration of the water cooling channels. The rod 10 is positioned within the rod holder 12 as shown in FIGS. 1 and 2 with a dove-tailed slot 14 being utilized for disconnecting the rod holder 12 from the supporting structure which is not shown in the drawing.
By referring to FIG. 2 of the drawing it can be seen that a plurality of water cooling channels 16 and 18 are formed on either side of a wearing surface 20 upon which the cylindrical rod 10 rides during the coating operation. In operation cooling water is circulated through the water cooling channels 16 and 18 by means of a cooling water inlet 22 and is removed from the rod holder by means of the cooling water outlet 24. The cooling water inlet 22 and the cooling water outlet 24 are internally connected to the water cooling channels 16 and 18 by means well known in the art and are not detailed in the prior art views FIGS. 1 and 2 for purposes of clarity.
It can be seen by referring again to FIG. 2 of the drawings that whenever the rod 10 is utilized in the coating operation against a paper web 26 positioned against a backup roll 28, that a downward force will be exerted on the wearing surface 20. The downward force is shown by the arrow 30 and results in extreme wear occurring on the wearing surface 20 and also results in water leakage occurring at the side surfaces 32 and 34 whenever excessive wear occurs on the wearing surface 20.
Another problem utilizing the prior art rod holders shown in FIGS. 1 and 2 occurred whenever sufficient water was attempted to be forced into the holder through the cooling water inlet 22. Because of the internal design of the water cooling channels 16 and 18, it was difficult to carry the cooling water the necessary 14' across the length of the rod holder. Multiple inlets and outlets were attempted and the water cooling channels 16 and 18 were deepened in order to attempt to minimize the problem but without any satisfactory results.
Another problem occurred with the prior art type holder shown in FIGS. 1 and 2 in that the rod 10 had to be inserted through the end 36 of the rod holder 12 because the rod 10 was designed to be positioned below the center points of the rod within the holder at the surfaces 32 and 34 as shown in FIG. 2 of the drawing. This problem also resulted in longer change-out times being required in withdrawing a worn rod 10 from the rod holder 12 by withdrawing it out the end 36 of the rod holder.
A pre-examination search of the Applicants' new and novel improved rod holder resulted in several patents being uncovered which show various configurations of rod holders but are not felt by the Applicant to be especially pertinent to his invention. The prior art type rod holder previously alluded to in the specification and shown in FIGS. 1 and 2 of the Applicants' drawing are typified by the U.S. Pat. No. 3,817,208, issued to Wolfgang Barnscheidt et al on June 18, 1974. This patent utilizes a rod holder which includes a body of elastomeric polyurethane and longitudinal grooves 7 and 8 for carrying, cleaning and lubricating liquid, such as water. The holder has a mounting portion 2 and a rib 3 which is received in a groove a the member 5. A modification of this type prior art rod holder is shown in the U.S. Pat. No. 3,701,335, issued to Wolfgang Barnscheidt on Oct. 31, 1972 wherein there is shown a rod 3 which is rotatably embedded in a confined body of elastomeric polyurethane or synthetic rubber. Lubricant and cooling fluid is fed by means of the conduit 7 to axial grooves 10 which are positioned on the side of the axial line of pressure from the rod coater with the fluid being discharged beyond the sides of the apparatus.
Several patents uncovered in the prior art search disclosed rod coaters wherein non-cooling channels were formed for purposes different than the Applicants' invention and these are typified in the U.S. Pat. No. 3,304,910, issued to E. Warner on Feb. 21, 1967; the U.S. Pat. No. 2, 774,329, issued to R. V. Smith on Dec. 18, 1956; the U.S. Pat. No. 3,271,187, issued to R. J. Chen et al on Sept. 6, 1966 and the U.S. Pat. No. 3,387,585, issued to J. J. Farrell on June 11, 1968.
In addition to the above patents, several patents were uncovered in the search wherein no cooling water channel was formed below the doctor rod and these are typified by the U.S. Pat. No. 3,785,340, issued to Larry O. Stafford et al on Jan. 15, 1974; the U.S. Pat. No. 3,029,779, issued to L. Hornbostel on Apr. 17, 1962; the U.S. Pat. No. 2,334,102, issued to T. A. Kauppi et al on Nov. 9, 1943 and the U.S. Pat. No. 2,695,004, issued to W. J. Montgomery et al on Nov. 23, 1954. The remaining patent uncovered in the prior art search disclosed a doctor system suction apparatus which was mountable along a doctor blade to provide an inlet for removing debris from the surface of the doctor blade and is shown in the U.S. Pat. No. 3,526,017, issued to W. Kleimola on Sept. 1, 1970.